Asymmetrically synchronous reduction and assembly of graphene oxide film on metal foil for moisture responsive actuator

Graphene has drawn tremendous attention for the fabrication of actuators because of its unique chemical and structural features. Traditional graphene actuators need integration with polymers or other responsive components for shape-changeable behaviour. Searching for a sole material with asymmetric properties is difficult and challenging for actuators that are responsive to external stimulus. Herein, asymmetrically synchronous reduction and assembly of a graphene oxide (GO) film with oxygen-containing group gradients was prepared on various metal foils. Such film possessed asymmetric surface chemical components on both sides, which showed reversible deformation via alternating moisture. Importantly, we can detect the moisture change via recording the voltage pulse during self-deformation on the basis of spontaneous H₃O⁺ ions diffusion across the GO film without the need of power input. Finally, a smart gripper was developed using a moisture responsive GO film. Present work opens a new avenue for developing smart actuator using a sole material and simultaneously realizing the detection of deformation in self-powered mode.